Struggling with chatter on semi-tall profile finish pass, help! - Page 2
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  1. #21
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    Any way you can pack material like bearing balls around the work. I remember a tool maker telling me that he would pack "dog shit" around die punches to keep them from singing during sharping.

    Tom

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    I run my long 1/2" 3F x 2"LOC at 2000 rpm and 20 IPM which seems a happy enough spot. Maritool finisher in a sidelock.

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    Since this is a repeat job I suggest getting an aluminum specific 5 fluter from Harvey for the next time you do these. They are a damn interesting end mill, pretty free cutting with a big solid core for stiffness. I have buried the 3/16"x.57" loc version pretty bad a few times and it just kept cutting, well worth trying out.

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  5. #24
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    Quote Originally Posted by TDegenhart View Post
    Any way you can pack material like bearing balls around the work. I remember a tool maker telling me that he would pack "dog shit" around die punches to keep them from singing during sharping.

    Tom
    This one is confusing the heck out of me - bearing balls? It sounds "exciting", but not ideal when milling a finish profile.

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    Quote Originally Posted by Milland View Post
    If all else fails, grind a small flat on the shank and try a sidelock.

    The small inherent eccentricity in a sidelock, not to mention the variable stiffness due to how a sidelock works, may break up harmonics that cause chatter.

    Use some of the existing test pieces to work out final parameters, don't keep cutting fresh metal until you're close.

    And order some more endmills, of a few different flavors. Sometimes brand S will work better than H, or G, or...

    Oh, yeah - when was the last time you checked drawbar force on that spindle?
    I think the harmonics are in the diving board he's machining. I don't think anything he does to the tool will fix it.

    CarlBoyd

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  8. #26
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    Quote Originally Posted by Milland View Post
    This one is confusing the heck out of me - bearing balls? It sounds "exciting", but not ideal when milling a finish profile.
    Perhaps I don't understand the problem. It sounded to me like he was trying to finish the inside of a wall, but not the outside as in a pocket. If it is a blade or similar that's finished on all sides, then this is off no value.

    The point I was trying to make is sometimes the vibration is a resonance of the work and no amount of setup will change it.

    Tom

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    Quote Originally Posted by TDegenhart View Post
    Perhaps I don't understand the problem. It sounded to me like he was trying to finish the inside of a wall, but not the outside as in a pocket. If it is a blade or similar that's finished on all sides, then this is off no value.

    The point I was trying to make is sometimes the vibration is a resonance of the work and no amount of setup will change it.

    Tom
    It looks like he got something to work well enough for him.

    Still, on the same train of thought that you've started with packing with dogshit, I bet you could get it to work better if you finish the walls first, then M0. Then clamp on some custom mini "C-Clamp" on the width of the part, then have the tool come in and finish the radii at the ends of the part. You'd be adding mass to the part, changing frequencies. And I think with a larger mass up high, you'd get a fair less squealing while traveling around the ends.

    Would be annoying to have to stop at M0 but hey. It's another potential workaround.

    There's gotta be 50 different solutions to this problem.

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    Quote Originally Posted by dandrummerman21 View Post
    There's gotta be 50 different solutions to this problem.
    How many machinists are there? That's how many solutions exist.

    [Actually, much more of course]

    It's one of those stupid things were you could take the part, the program, the cutter, etc., and mount it in an identical second machine and it would cut fine.

    Tiny differences in bearing preload, drawbar stiffness, spindle mass - any could reshape the resonance peaks of the machine to make this a non-issue.
    Last edited by Milland; 05-13-2021 at 06:50 PM.

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  12. #29
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    Quote Originally Posted by TDegenhart View Post
    Perhaps I don't understand the problem. It sounded to me like he was trying to finish the inside of a wall, but not the outside as in a pocket. If it is a blade or similar that's finished on all sides, then this is off no value.

    The point I was trying to make is sometimes the vibration is a resonance of the work and no amount of setup will change it.

    Tom
    The way I've imagined it is a stub sticking up from a thicker section, but I've not considered it being inside a larger block or in some other way benefiting from external supports like a BB fill. But I think I understand what you were going for now.

    We never get pictures, dang it...

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    Quote Originally Posted by CarlBoyd View Post
    I think the harmonics are in the diving board he's machining. I don't think anything he does to the tool will fix it.

    CarlBoyd
    I think you are exactly correct Carl!

    Quote Originally Posted by Milland View Post
    The way I've imagined it is a stub sticking up from a thicker section.

    We never get pictures, dang it...
    Exactly. It is essentially a 1.112" x .312" x 1.410" tall rectangle boss.
    Of which 3 sides and all 4 rads die into the floor with a sharp inside corner. The 4th side is flush with the outside of the part.

    Then, in a subsequent OP, 80% of the whole thing goes away leaving two small "legs".

    I'll snap some pics and try to find time to post them from my lap-top. I can't post pics from the shop PC anymore. Don't know why?

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    Quote Originally Posted by wheelieking71 View Post
    Picky customer (getting pickier). I deliver in the white. He doesn't want to see any visible evidence of steps.

    Vibratory finisher.


    --------------

    Think Snow Eh!
    Ox

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    Quote Originally Posted by Ox View Post
    Vibratory finisher.


    --------------

    Think Snow Eh!
    Ox
    Interesting. You mean throw the customer into the vibratory finisher and shake some sense into him?

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    Quote Originally Posted by Orange Vise View Post
    Interesting. You mean throw the customer into the vibratory finisher and shake some sense into him?
    "finisher" sounds kind of a more definitive end to the problem...

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    It could be the endmill. Did you try a different MA ford endmill? If the cylindrical margin is wrong or slightly too large it will cause a lot more force to be applied into the part.
    On flimsy parts I've had good luck cutting to size in say 2-3 depths and then just taking a spring pass at the bottom.

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  21. #35
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    I would try a rougher/finisher variable flute like this rougher/finisher variable flute end mill for aluminum I have had great results with these in skinny unsupported walls in Delrin.

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    Quote Originally Posted by dstryr View Post
    It could be the endmill. Did you try a different MA ford endmill? If the cylindrical margin is wrong or slightly too large it will cause a lot more force to be applied into the part.
    On flimsy parts I've had good luck cutting to size in say 2-3 depths and then just taking a spring pass at the bottom.
    I tried exactly that at one point Dennis. Chatter on the spring pass was deafening! It was one of those cuts that definitely wanted some chip.
    And, yes, I did swap a new tool in as a sanity check. No difference.

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    Quote Originally Posted by Ox View Post
    Vibratory finisher.


    --------------

    Think Snow Eh!
    Ox
    See, this is what is frustrating. He bead-blasts them!

    I have probably made them 30 times before. And I have always finished this feature in Z steps.
    Actually I just roughed to size with an 1-1/4" indexable. Parts were perfect. But, you could see those "tiger stripes".
    Ha asked me to make them go away. Even though, he makes them go completely away with zero evidence when he blasts.
    I'm not one to argue with customers though. Especially right now.
    And, double especially since he just rejected the ones I just delivered that I subbed out to a good buddy of mine because I was buried.

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    Some pics:

    img_2756.jpg

    img_2755.jpg

    img_2757.jpg

    img_2758.jpg

    img_2759.jpg

  25. #39
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    Get a media blaster and offer to perform that service too.

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  27. #40
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    Quote Originally Posted by wheelieking71 View Post
    Some pics:

    img_2756.jpg

    img_2755.jpg

    img_2757.jpg

    img_2758.jpg

    img_2759.jpg
    If you can, I'd add another operation and put the part in a vise where the back face (the side that your thumb is touching) is against the vise jaw, and the moveable jaw clamps on the 2 posts. Then skin those 2 posts. Shouldn't have any chatter that way. Is that the only trouble area?


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